Field of the Invention
This application is generally directed to a selective, mycoherbicide formulation for killing ungerminated seeds of invasive grass species.
Description of the Related Art
Annual grass weeds cause large yield losses in intensive agriculture, and more importantly from a Forest Service perspective, are principal contributors to environmental degradation on vast acreages of public land in the western United States. Federal, state, and local public landowners, as well as private landowners, and in particular winter cereal grain producers, suffer this condition in one of our most important resources—our land. This condition is present in millions of hectares of land that are important to rangeland, and also in cropland, for example. Moreover, not only do these weeds take over the land, they also add substantially to the fire hazard in semi-arid and arid regions. As such, the art would appreciate a method of treating soil to prevent, inhibit, or eliminate stands of invasive grass species in such areas, and particularly, a method of restoring semi-arid and arid rangeland.
A major obstacle to seeding success with native species as part of post-burn rehabilitation in arid and semi-arid shrubland ecosystems is competition from exotic annual brome grasses such as cheatgrass (Bromus tectorum) and red brome (Bromus rubens). In many cases, these are the same grass species that fueled the shrub-destroying fire. Seed banks of annual bromes are depleted but usually not completely destroyed by burning. The common wisdom is to seed as quickly as possible after the fire that destroys the shrub overstory, in order to give the seeding a chance to establish before annual brome competition builds back up. In arid and semi-arid ecosystems, seedings often fail because of inadequate precipitation, and this window of opportunity closes quickly. Once annual bromes reestablish dominance after the shrub-destroying fire, it becomes very difficult to seed successfully on these sites, even if they reburn. This is because more brome seeds survive fire when hot-burning woody fuels are no longer present. If we could find a way to destroy the residual annual brome seed bank after fire, the probability of successful rehabilitation would be greatly increased, and even sites that (i) have burned many times and (ii) are in persistent annual brome monocultures could perhaps be seeded successfully.
The options available for control of annual brome grasses in arid and semi-arid wildland ecosystems are limited, and each has disadvantages. The options include, for example, burning, tillage, and the application of pre- and post-emergence chemicals (herbicides). Early season burning, before seed dispersal, can eliminate most current-year seeds, but there may still be carryover seeds in the seed bank, and these seeds can provide significant competition for seeded species in the years following treatment. Also, prescribed burning in these ecosystems is risky and raises other issues, such as air quality. Tillage after annual brome emergence is too expensive to undertake on large acreages, damages remnant perennials, and causes soil disturbance. Herbicides tend to be expensive, and selectivity of the herbicides also poses concern, as well as the length of time that they can negatively impact the environment after application. The detailed, habitat-specific research needed to understand herbicide impact on non-target species is often not in place to guide management. And, there are many policy issues surrounding the use of herbicides.
One of skill will appreciate that the current practices of controlling brome grass have several problems. A major problem to note, however, is that currently available methods do little or nothing to eliminate ungerminated seeds, and since annual grass weeds respond dramatically to increases in available resources, even a few ungerminated carryover seeds can quickly re-establish a population. As such, an effective control for these grass weeds should include elimination of this bank of ungerminated seeds.
Accordingly, one of skill will appreciate a biocontrol method for elimination of annual grass weed persistent seed banks in rangeland and cropland, the method (i) reducing or eliminating the repeated or extensive use of fire, tillage and chemicals and the environmental effects of such use; (ii) reducing costs; (iii) increasing target selectivity; (iv) facilitating use on large acreage; (iv) functioning to reduce or eliminate seed carryover from a persistent seed bank; and, namely, (v) eliminating or otherwise controlling banks of ungerminated seeds. There is currently no other biocontrol method for killing ungerminated seeds.